A system for regulating the idling speed of an internal-combustion engine is described in German Published Patent Application No. 33 29 800 (corresponding to U.S. Pat. No. 4,554,899). A system for the closed-loop control of the idling speed of an internal combustion engine, in particular a self-ignitable internal-combustion engine, by means of an adaptive controller is described therein. This controller contains a proportional, an integral, and a differential component. The response characteristic of the controller is able to be adjusted dependent upon the rotational speed. The dynamic performance of this device is not optimal. Thus, in certain operating states, the rotational speed may drop below the nominal idling speed. This is referred to as undercutting and should be prevented. Furthermore, various operating states exist with different controller action. Unsteadiness can occur when the transition is made from one operating state to another operating state with another controller action.
An object of the present invention is to improve the dynamic performance of a system for regulating the idling speed of an internal-combustion engine.